Flat screen for pulp screening



April 29, 1952 B. COWAN ETAL 2,594,400

FLAT SCREEN FOR PULP SCREENING Filed Nov. 19, 1949 3 Sheets-Sheet 2 April 1952 B. COWAN ETAL 2,594,400

FLAT SCREEN FOR PULP SCREENING Filed Nov. 19, 1949 3 Shets-Sheet 3 Irzvemn jerg 6 0 wan $1.27 2 z ufi (bu/072 Patented Apr. 29, 1952 FLAT SCREEN FOR-PULP SCREENING nemcowan and Elijah cowan, Montreal,

- Quebec, Canada Application November 19, 1949;Serial No. 128,316

2 Claims. (CI; 92-32) This invention relates to improvements in flat screening aqueous suspensions of fibers in the preparation'of pulp and paper-making stock.

" One'object of the invention is theprovision of agenerally" improved screen assembly of lowhead construction thereby reducing the head room required for installation of the screen.

' Another object of the invention is to provide a "unit type of screen which may be combined with T'Isimilar units to provide a screen assembly of "any desired capacity characterized by reduced construction and replacement costs. A further objectisto provide, in a flat screen of the diaphragm type, improved sealing means for preventing leakage between the walls of the diaphragm chamber and the marginal portions of the diaphragm operating therein.

A further object of the invention is to provide a generally improved flat screen of the diaphragm type in which the diaphragm is supported from the Walls of 'the diaphragm chamber by flexible sealing and supporting means so that the diaphragm operating or vibrating mechanism is relieved of the weight of the diaphragm and may therefore be made of light weight materials to reduce inertia loads.

A further object is to provide, in a flat screen of the diaphragm type, flexible and resiliently compressible diaphragm supporting and seal-' ing means which acts as a rubber spring flexibly supporting the marginal portions 'of .the diaphragm in such manner as to prevent or reduce to a minimum the rocking or uneven motion of the diaphragm which often nullifies the vibration of the usual types of vibrating mechanisms employed for operatingthe diaphragm.

Other objects, advantages and characteristic features of the invention will be more readily understood. from the following description taken in connection with the accompanying drawings,

in which Fig. 1 is a view partly in top plan and partly in horizontal section of a screen unit or assembly embodying the invention.

Fig. 2 is a view partly in side elevation and partly-in -vertical section, the plane of the section being indicated by the section line B--B in Fig. 3.

Fig. 3 is a vertical sectional view taken along the section line 33 of Fig. 2; and

Fig. 4 is an enlarged detail view of a sealing means employed for supporting" and sealing the diaphragm element of the screen.

Referring more particularly to the drawings, 5 designates a generally rectangular frame which forms the side and end walls of a diaphragm chamber 6. In the present instance, frame 5 is shown as'bein'g composed of structural teel shapes 5a arranged'in rectangular forma- --Isc'reens of the diaphragm type employed, for V example, in the pulp and paper industry for "2 tion and weldedtogether. However, it will be understood that'frame 5 maybe formed'jb'yany suitable type of frame'members secured'together "ei'ther by welding or bolting.

' A screenvat l is supported on and fastened to frame 5 by bolts 8 and nuts 9. As'here' shown,

the'va't'l is formed with outwardly directedbottom flanges H) which rest upon and are"secured to outwardly directed top flanges H of frame 5 by'the bolts 8 and nuts 9. The bottom of vat "l is formed'by four screen plates I2 which rest on supports l3 afforded by the frame and are retained in place by holding down strips and I5 secured to the underlying screen supports 13 by fastening screws [1.

' the diaphragm chamber and the other is used as a clean out opening which is covered by a closure plate. In the present instance, the opening 20 is shown covered by a plate 22 to serve as a clean-out opening while the other opening 20a. is left uncovered to serve as a discharge port for screened stock.

Since the cover plate 22 may be applied to either of the openings 28 and 29a, it will be seen that the accepted stock discharge can be from either side of diaphragm chamber 6.

Frame 5 is supported in elevated relation to a floor surface S b suitable corner supports such asthe H-shaped structural steel members indicated at 24.

The mechanism for vibrating diaphragm l3 includes a shaft'26 journalled in roller bearings 27 mounted on a frame structure 28 supported by and between the corner supports 24. The central portion of shaft 25 carries a rigidly attached eccentric sleeve 30 on which a housing 3! is mounted by a roller bearing 32. .iThe

housing 3| is formed with a flat upper portion 33 to which a covering plate 34 is secured by bolts 35. A block 36 composed of rubber or similar resiliently compressible'material is confined between the plate 34 and an opposing plate 31 which is fastened to the under side of the central portion of diaphragm l3 by suitablbolts 38. The plates 34 and3l are bonded to the interposed rubber blocks 36 and form therewith what may be termed a flexible rubber connecting link between the diaphragm i3 and the eccentric operating mechanism represented by the eccentric sleeve 30 and the housing 3!. The

' advantage of this method of connecting the diaphragm and the shaft operated eccentric mechabsorb the rotary motion component of the eccentric mechanism and to ensure a straight line vertical motion of the diaphragm in response to operation of the eccentric mechanism. One end of shaft 26 is fastened by a coupling 4|! to a shaft 4| which is journalled in anti-friction bearings 42 mounted on pillow blocks 43. Shaft 4| carries a sheave 44 which is driven by a V-belt drive connection 45 from a sheave 46 mounted on the shaft 4'1 of an operating motor 48.

The sealing means l9 provided for supporting and sealing the diaphragm |8 constitutes a vitally important feature of the invention. As here shown, this sealing means comprises upper and lower continuous, resiliently compressible, sealing members 5| of rectangular form compressed against the upper and lower sealing surface of a continuous sealing tongue 52 projecting outwardly from the marginal portion of a rigid metal diaphragm l8 and terminating in spaced relation to the surrounding wall portions of frame 5. The sealing tongue 52 is located substantially midway between the upper and lower surface of diaphragm I8 and the thickness of the sealing members 5| is preferably such that these members do not project any substantial distance above or below the top and bottom surfaces of the diaphragm. The sealing members 5| are arranged between and supported by upper and lower retaining plates 53 which are fastened to the upper and lower surfaces of an inwardly projecting flange-forming portion 54 of frame member 5 by suitable fastening bolts 55 and nuts 56.

Each of the sealing members 5| is composed of a central portion or core 58 made of sponge rubber and covered by a thin covering 59 of solid rubber. Suitable rubber spacers 60 are interposed between the opposingportions of the sealing members 5| which lie outwardly of sealing tongue 52.

Spacers or shims 6|, made of wood or other suitable material, are interposed between the inwardly projecting portion 54 of frame 5 and the lowermost retaining plates 53 of the sealing means l9 to regulate the effective pressure exerted by the plates on the interposed sealing members 5| when the pressure applying nuts 56 are tightened. The thickness of the shims 6| should be such as to (1) ensure water tightness between the frame 5 and the diaphragm l8 and (2) ensure that the weight of the diaphragm, instead of being borne by the housing 3| of the eccentric operating mechanism, is transferred to and borne by the frame 5 which supports the sealing members l9.

The herein described method of supporting the weight of the diaphragm I!) from the frame 5 through the agency of the sealing means I9 relieves the eccentric mechanism and the drive shaft 26 of considerable load and reduces both stress and wear.

It is also important to note that the present invention provides a screen unit in which a group of screen plates |2, preferably four in number, are served by a single diaphragm. A unit of this type may be combined with similar four plate units to provide an assembly which will give any desired screening capacity at reduced construction and replacement costs compared with any known assembly for obtaining similar capacity.

Having thus described the nature of the present invention and a preferred embodiment thereof, it will be understood that various modifications may be resorted to within the scope and spirit of the invention as defined by the appended claims. For example, the shaft operating the eccentric mechanism may be connected to the diaphragm by any suitable form of connecting means in which rubber or other resiliently compressible material is incorporated in such'manner as to absorb the rotary motion component of the eccentric mechanism and to ensure a straight line vertical motion of the diaphragm in response to operation of the eccentric mechanism.

We claim:

1. In a flat screen of the diaphragm type, a frame structure forming the marginal walls of a diaphragm chamber, a rigid movable diaphragm forming the bottom wall of said chamber and provided with a continuous outwardly projecting sealing tongue extending around and formed integral with the marginal edge of the diaphragm, said sealing tongue presenting continuous upper and lower horizontal sealing surfaces and being separated from surrounding wall portions of said frame by an intervening gap, upper and lower resiliently compressible sealing members bridging said gap and extending continuously around the marginal edge of the diaphragm in sealing and supporting engagement with the upper and lower sealing surfaces of said tongue, and retaining members between which said sealing members are arranged and supported in sealing contact with the marginal walls of the diaphragm chamber, said retaining members being secured to and supported by said frame structure.

2.,In a fiat screen of the diaphragm type, a frame structure forming the marginal walls of a diaphragm chamber, a rigid movable diaphragm forming a bottom wall portion of said chamber which is separated from the marginal walls of the chamber by an intervening gap and resiliently compressible diaphragm supporting and sealing means closing said gap and affording a yieldable supporting means for movably supporting said diaphragm from the marginal walls of said chamber, said flexible sealing means comprising upper and lower resiliently compressible sealing members of substantial thickness and compressibility extending around the diaphragm and closing the gap between the diaphragm and the marginal walls of said chamber, a continuous sealing tongue formed integral with the marginal edge of the diaphragm and fitted between said sealing members in sealing engagement therewith, upper and lower pressure applying retaining members between which said sealing members are arranged and supported, said retaining members being fastened to and supported by the marginal walls of said chamber by fastening means operable to effect pressure applying adjustment of said retaining members to regulate the pressure contact between the sealing members and said sealing tongue.

BEN COWAN. ELIJAH COWAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 242,428 Bremaker June '7, 1881 FOREIGN PATENTS Number Country Date 9,995 Great Britain 1897 

